Delay line with recessed support to prevent shorting by metal sputtering



F. DIAMAND March 12, 1968 DELAY LINE WITH REGESSED SUPPORT TO PREVESHORTING BY METAL SPUTTERING Filed July 12, 1963 ndE INVENTOR: F/ixo/Amuvo BY I ATTORNEY;

United States Patent T DELAY LINE WITH RECESSED SUPPORT TO PREVENTHORTING BY METAL SPUTTERING Felix Diamand, Paris, France, assignor toCSF-(Jompagnie Generale de Telegraphic Sans Fil, Paris, France FiledJuly 12, 1963, Ser. No. 2%,633 Claims priority, application France, Aug.23, 1962, 907,603, Patent 1,338,984 4 Claims. (Cl. 333-41) The presentinvention relates to delay lines utilized in hyperfrequency electrontubes, and more particularly to delay lines destined for very highfrequencies and therefore having very small dimensions.

It is known that a high mechanical precision and indeformability arerequired of a delay line in order that the tube may correctly operate.These conditions are the more difficult to satisfy the higher thefrequencies of operation and, consequently, the more the calculations ofthe delay line lead to smaller dimensions which diminish the mechanicalrigidity and sturdiness.

It has already been proposed heretofore to resolve this difficulty byaffixing the line to an insulating base, for example, by forming thesame by photogravure on a plate. This structure, however, presents theinconvenience that as a result of unavoidable sputterings of the metalof the line, disintegrated or evaporated in part by the impact on theline of electrons of the beam, there is formed a conductive deposit onthe relatively cold surface of the insulating base between the metallicelements of the line, producing at a more or less short interval ashort-circuit harmful to the operation.

The object of the present invention is an improvement for the type ofdelay lines secured to an insulating base, and intended to remedy theaforementioned inconvenience.

According to the present invention, the insulating base has no longerthe form of a plate as in the known structures but is cut in the mannerto follow the form of the periodic elements of the line. A line ofmeander shape will therefore be secured to an insulating base also ofmeander shape or on a series of parallel insulating bars, aninterdigital line on an insulating base in the form of interleavedcombs, of a ladder or also on a series of parallel insulating bars, etc.

Accordingly, it is an object of the present invention to provide a delayline which effectively avoids, by simple means, and in a reliable mannerthe shortcomings noted hereinabove in connection with the prior artconstructions.

It is another object of the present invention to provide a delay line ofthe type mentioned hereinabove, particularly a delay line for use athyperfrequencies, which effectively avoids the danger of short-circuitsas a result of sputtering of metal due to electron bombardment of theline.

Still a further object of the present invention resides in the provisionof a very high frequency wave-guiding structure of the type mentionedhereinabove which is mechanically sturdy, may be readily machined andassembled yet assures proper operation for relatively long periods oftime.

These and other objects, features and advantages of the presentinvention will become more obvious from the following description whentaken in connection with the accompanying drawing which shows, forpurposes of illustration only, several embodiments in accordance withthe present invention and wherein:

FIGURE 1 is a partial longitudinal cross-sectional view of a prior artdelay line, intended to explain the shortcomings, thereof;

3,373,382 Patented Mar. 12, 1968 FIGURE 2 is a partial longitudinalcross-sectional view, similar to FIGURE 1, of a delay line in accordancewith the present invention;

FIGURE 3 is a partial horizontal cross-sectional view of a delay linethat may be utilized in FIGURE 2, and

FIGURE 4 is a partial horizontal cross-sectional view, similar to FIGURE3, and illustrating the insulating base adapted for use with the delayline of FIGURE '3.

Referring now to the drawing wherein like reference numerals are usedthroughout the various views to designate like parts, and moreparticularly to FIGURE 1 showing a cross-sectional view through a knowndelay line structure, reference numeral 1 designates therein a delayline which is fixed to an insulating base 2 in the form of a plate. Theinsulating base 2 itself is fixed to a metallic back-plate 3.

In this prior art structure, the sputterings of the metal of the line 1fall on the relatively cold surface of the base 2 and form thereon adeposit 4 which short-circuits after a more or less short lapse of timethe periodic elements of the delay line.

FIGURE 2 shows in cross section a delay line structure according to thepresent invention in which this inconvenience is avoided. In FIGURE 2,the delay line 1, for example, of copper and of meander shape, as isindicated by the horizontal cross-sectional view thereof in FIGURE 3, isno longer fixed on a plate 2 but on an insulating base 5, for example,of alumina, cut into meander shape like the line 1, the horizontal crosssection of this insulating base 5 being shown in FIGURE 4. Theinsulating base 5 is secured on a metallic back-plate 3, for example,made of copper as in FIGURE 1. The manufacture of this assembly maycomprise, for example, the preliminary and separate cutting of the line1 and of the base 5, and the securing of one to the other by brazing. Asan example of a modification, one could also simultaneously machine ametallic leaf or thin plate covering an insulating plate, the coveringbeing made electrochemically, by pulverization or any other knownmanner.

As shown in FIGURE 2, the deposit 4, due to the metallic sputterings,occurs in this embodiment in the same manner as in FIGURE 1. However, incontradistinction to the embodiment of FIGURE 1, the deposit 4 of FIGURE2 is formed directly on the metal of the back-plate 3 and is insulatedfrom the metal of the delay line 1 by the thickness of the base 5. It istherefore no longer harmful as in the preceding case.

While I have shown and described one embodiment in accordance with thepresent invention, it is of course understood that the same is notlimited thereto, but is susceptible of numerous changes andmodifications as known to a person skilled in the art. For example, thepresent application is also applicable to any other form of known delayline with back-plate, interdigital line, ladder-type line, etc. Thedimension d of the elements of the insulating base (FIGURE 4) need notbe exactly equal to that of the elements of the delay line as shown inthe drawing but may also be different therefrom, either larger orsmaller. The portions A, B, C, and D of the meander of FIGURE 4 may alsobe suppressed whereby the meander is thus replaced by a series ofparallel insulating bars. It is understood that all the delay linescomprising such modifications obvious to a person skilled in the art areequally within the spirit and scope of the present invention.

Thus, it is obvious that the present invention is not limited to thedetails shown and described herein but is susceptible of numerousmodifications as pointed out above, and I therefore do not wish to belimited to the details shown and described herein but intend to coverall such changes and modifications as are encompassed by the scope ofthe appended claims.

I claim:

1. In an evacuated tube electron discharge device having a delay line ofgeometrically periodical structure subject to metal sputtering, saiddelay line comprising an insulating base, a series of spaced metalelements fixed on said insulating base, and a conductive support forsaid base, said insulating base being provided with cut-out portions inthe spaces between said elements sufficient to bare the surface of saidconductive support within said spaces and cause the insulating base toconform substantially to the shape of the spaced metal elements.

2. In an evacuated tube electron discharge device having a delay line ofgeometrically periodical structure subject to lnetal sputtering, saiddelay line comprising an insulating base, a series of spaced metal rungsfixed to said insulating base, a conductive support for said base, saidbase having a shape conforming susbtantially to the shape of the spacedmetal rungs including at least a series of insulating rungs eachsupporting a respective metal rung of said delay line, thereby leavingexposed parts of the surface of said conductive support in the spacesbetween said rungs.

3. In an evacuated tube electron discharge device having a delay line ofgeometrically periodical structure subject to metal sputtering, saiddelay line comprising an insulating base, a series of spaced metal rungsfixed to said insulating base, a conductive support for said base, saidbase having a shape including at least a series of in- 4 sulating rungseach supporting a respective metal rung of said delay line, therebyleaving exposed parts of the surface of said conductive support in thespaces between said rungs, and the width of said metal rungssubstantially coinciding with the width of said insulating rungs.

4. In an evacuated tube electron discharge device, a wave-guidingstructure having a plurality of geometrically periodical elementssecured to an insulating base which in turn is fixed to a conductivesupport,

the improvement essentially consisting of conforming the insulating basesubstantially to the shape of the delay elements at least in part tothereby leave exposed parts of the surface of the conductive support inthe spaces between the delay elements and avoid short circuits as aresult of metallic deposits caused by sputtering of the metal from thedelay elements.

References Cited UNITED STATES PATENTS 2,704,829 3/1955 Clay 333*313,173,111 3/1965 Kallmann 333-31 3,257,629 6/1966 Kornreich 333-31FOREIGN PATENTS 767,077 1/ 1957 Great Britain. 708,601 5/1954 GreatBritain.

ELI LIEBERMAN, Primary Examiner.

1. IN AN EVACUATED TUBE ELECTRON DISCHARGE DEVICE HAVING A DELAY LINE OFGEOMETRICALLY PERIODICAL STRUCTURE SUBJECT TO METAL SPUTTERING, SAIDDELAY LINE COMPRISING AN INSULATING BASE, A SERIES OF SPACED METALELEMENTS FIXED ON SAID INSULATING BASE, AND A CONDUCTIVE SUPPORT FORSAID BASE, SAID INSULATING BASE BEING PROVIDED WITH CUT-OUT PORTIONS INTHE SPACES BETWEEN SAID ELEMENTS SUFFICIENT TO BARE THE SURFACE OF SAIDCONDUCTIVE SUPPORT WITHIN SAID SPACES AND CAUSE THE INSULATING BASE TOCONFORM SUBSTANTIALLY TO THE SHAPE OF THE SPACE METAL ELEMENTS.